Myocardial Infarction, Acute (AMI)/ST Elevation Myocardial Infarction (STEMI)

Description

Emergency Treatment

Referral

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ICD 10 code: I21.0-3/I21.9/I22.0-1/I22.8-9/I24.8-9/I25.6/I25.8-9

DESCRIPTION

AMI/STEMI is caused by the complete or partial occlusion of a coronary artery and requires prompt hospitalisation and intensive care management.

The major clinical feature is severe chest pain with the following characteristics:

• Site: retrosternal or epigastric
• Quality: crushing, constricting or burning pain or discomfort
• Radiation: to the neck and/or down the inner part of the left arm
• Duration: at least 20 minutes and often not responding to sublingual nitrates
• Occurrence: at rest

May be associated with:

• Pallor 
• Pulmonary oedema
• Sweating 
• A decrease in blood pressure
• Arrhythmias

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Note
Not all features have to be present

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EMERGENCY TREATMENT

Before transfer

Cardio-pulmonary resuscitation if necessary (See: Cardiac arrest – cardiopulmonary resuscitation)

• Oxygen 40% via facemask, if saturation < 94% or if in distress

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CAUTION

Do not administer oxygen to acutely ill patients who are not hypoxic (SPO₂ ≥ 96%)

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LoE:IIb²⁵

AND

• Aspirin, oral, 150 mg as a single dose (chewed or dissolved) as soon as possible

LoE:Ia²⁶

AND

• Nitrates, short acting, e.g.:
• Isosorbide dinitrate, sublingual, 5 mg, immediately as a single dose
  • May be repeated at 5-minute intervals for 3 or 4 doses

LoE:IVb²⁷

AND

• Morphine 10 mg diluted with 10 mL of water for injection or sodium chloride 0.9%, slow IV (Doctor prescribed)
  • Start with 5 mg; thereafter slowly increase by 1 mg/minute up to 10mg
  • Can be repeated after 4–6 hours if necessary, for pain relief
  • Beware of hypotension

AND

• Thrombolytic, e.g.: (see table for time window below): (Doctor initiated), e.g.:
• Streptokinase, IV 1.5 million units diluted in 100 mL sodium chloride 0.9%, infused over 30–60 minutes. Do not use heparin if streptokinase is given
  • Hypotension may occur. If it does, reduce the rate of infusion but strive to complete it in < 60 minutes
  • Streptokinase is antigenic and should not be re-administered in the period of 5 days to 2 years after 1st administration
  • Severe allergic reactions are uncommon but antibodies which may render it ineffective may persist for years

LoE:IIb²⁸

LoE:IIb²⁹

Considerations for initiating thrombolytics

Contra-indications

For acute myocardial infarction with ST elevation or left bundle branch block: - Maximal chest pain is ≤6 hours doctor to initiate treatment - If beyond 6 hours and chest pain, consult a specialist - >6 hours and no chest pain, thrombolytic not indicated. Manage as above and refer patient. LoE:Ia30

Absolute: - Streptokinase used within the last year - Previous allergy - CVA within the last 3 months - History of recent major trauma - Bleeding within the last month - Aneurysms - Brain or spinal surgery or head injury within the preceding month, or recent (<3 weeks) major surgery, - Active bleeding or known bleeding disorder - Aortic dissection   Relative (consult specialist): - Refractory hypertension - Warfarin therapy - Recent retinal laser treatment - Subclavian central venous catheter - Pregnancy - TIA in the preceding 6 months -Traumatic resuscitation

Table 4.2: Streptokinase therapy

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Note: 

Refer all suspected or diagnosed cases urgently

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Continuation of aftercare treatment initiated at higher level of care:

Continue therapy with appropriate lifestyle modification and adherence support

• Aspirin, oral, 150 mg daily (continued indefinitely in absence of contraindications)

LoE:Ia³¹

When clinically stable without signs of heart failure, hypotension, bradydysrhythmias or asthma:

• Cardio-selective beta-blocker, e.g.: (Doctor prescribed)
• Atenolol, oral, 50 mg daily

AND

• HMGCoA reductase inhibitors (statins), e.g.:
• Rosuvastatin, oral, 10 mg at night

LoE:Ia³²

Patients on protease inhibitor:

• Atorvastatin, oral, 10 mg at night

LoE:Ia³³

Patients on amlodipine (and not on a protease inhibitor):

• Simvastatin, oral, 10-20 mg at night

LoE:Ia³⁴

If patient complains of muscle pain:

Reduce dose e.g.:

• If simvastatin 20 mg not tolerated, reduce to 10 mg

LoE:Ia³⁵

OR

• Refer for further management

AND

If there is cardiac failure or LV dysfunction (Doctor initiated):

• ACE-inhibitor, e.g.:
• Enalapril, oral, target dose 10 mg 12 hourly (usually titrated from 2.5 mg 12 hourly)

LoE:Ia³⁶

Angioedema is a potentially serious complication of ACE-inhibitor treatment and if it occurs it is a contraindication to continued therapy or to re-challenge.

REFERRAL

Urgent

• All suspected or diagnosed cases

Click here for the pdf.

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Standard Treatment Guidelines and Essential Medicines List for South Africa, Primary Healthcare, 2020-2024_Version 1.0_1 November 2024

Chapter 4: Cardiovascular Conditions_4.4 Myocardial Infarction, Acute (AMI)/ST Elevation Myocardial Infarction (STEMI)